Fuse cartridge



Jul 27, 1965 F. HOLLMANN ETAL 3,195,521

FUSE CARTRIDGE Filed Sept. 19, 1960 2 Sheets-Sheet l Jnvenfors;

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United States Patent 3,l%,52l FUSE CARTREDGE Fritz Hollmann, Rheydt, Rhineland, and Hans Emmerich, Rheydt-Giesenklrchen, Germany, assignors to Fritz Driesclrer Spczialfahrilr fur Eiektriaitatswerltsbedarf, Rheydt, Rhlneland, Germany Filed Sept. 19, lhzil, Ser. No. 56,722;

Claims priority, application Germany, Apr. 4-, 196% 4 (Ilaims. (ill. 29-4555) Known fuse cartridges distributed in large quantities under the name of saftety fuses for low voltage, have a casing consisting of a tubular insulator enclosing the link and a suitable arc-quenching substance, and two metal plates or caps closing off the ends of the casing. These end plates or caps each bear a contact on the outside, for example, a knife terminal, or a clamp connectable to a knife terminal, and are joined together by the single or multiple fusible link attached to their inner faces. Often the end plates or caps are each provided in addition with a T-shaped appendage projecting radially outward beyond the periphery of the insulator to be engaged by an insulating handle for inserting the cartridge in and removin it from a socket without danger of touching live parts.

To unite the live parts of such a fuse cartridge with the tubular insulator, much equipment and manual labor are required. Since the end plates or caps must completely cover the end openings of the insulator, they cannot be passed through it, nor, therefore, be connected to each other by the fusible link before being united to the insulator. it is therefore common practice to attach smaller plates, capable of being passed through the insulator, to the ends of the link, thrust the resulting prefabricated fuse insert into the insulator, screw the end plates of this insert to the end plates or caps of the cartridge, and finally connect these end plates or caps firmly to the insulator with screws, cement or friction.

The object of the invention is to provide a fuse cartridge of the kind referred to, requiring only a minimum of individual parts for fuses of the said kind, their a sembly requiring no auxiliary equip sent and only a minimum of manual labor.

In the case of fuse cartridges having terminals located at opposite ends of the casing and a single or multiple link imbedded in an extinguisher and connecting the terminals, this is accomplished, according to the invention, by casting the casing in one hollow piece of synthetic resin tightly and firmly molded around the terminal ends fixedly attached to the link. Such a cartridge, accordingly, consists solely of the parts indispensable to a fuse, namely the two terminals, the link connecting them, and the one-piece housing, with optional addition of the two appendages for engaging an insulating handle. Manual and other preparatory operations are confined to joining the two terminals with the link into a prefabricated conductive unit, whereas the joining of this unit to the casing results automatically from the fabrication to the latter by casting. Experiments have shown that the terminals, which are subject to some mechanical stress, become quite firmly seated in the wall of the cast casing, especially when provided with rough spots, recesses or projections located Within the casing wall. The appendages with T-shaped or hammerhead ends for engaging a handle may be attached to the terminals in conventional manner, and likewise imbedded in casing material except for their exposed outside ends. However, the new type of fuse cartridge alternatively permits insertion of these appendages in the casing wall, advantageously in thickened parts thereof, in such manner that fz fllliifizl Patented July 27, 1965 they do not touch the terminals themselves and are thus electrically insulated from them.

A fuse of the kind described may be fabricated in various ways involving, in each instance, the consecutive formation of two bodies of nonconductive material in nested relationship about that part of the aforedescribed unit which includes the fusible link and the adjoining ends of the two terminal members. One method consists in that the link and terminals fixedly joined thereto are molded in an arc-quenching agent, with addition of a small quantity of binder that will not impair porosit and after the binder has set, the resulting molded quencher core and inner portions of the terminals projecting therefrom are enveloped with cast casing material in a suitably larger mold.

Another method, giving equally good results but more efficient in some cases, consists in that the outer casing or shell is centrifugally cast in a mold fitted with the link and terminals fixedly joined thereto, and thus at the same time united to the live parts, and after the casing material ie. a cyntheti resin) has set, the resulting casing is filled with qunching substance through a cored or drilled in the former case, two molds are required to make the fuse cartridge, one having a smaller cavity to receive only the link and terminals directly connected thereto. When this cavity has been filled with quenching substance to which a small quantity of binder has been added, and when the binder has set, the mold is replaced by another with larger cavity, in which the core and the inner portions of the terminals projecting from it are enveloped with casing material. In this mold, appendages for the handle, either attached to the terminals or inserted loosely before the mold is closed, may also be imbedded to h an extent that only their T-shaped or hammerhead e; .c nities project from the casin From making the cartridge casing by centrifugal casting, a suitable device consists of a mold receiving the link and terminals and having two projecting gudgeons on the same centenine as the cartridge, by means of which the mold is rotatably mounted in a frame; this frame in turn is rotationally driven about a shaft perpendicular to the centerline of the gudgeons, and has a disk which is centered on its axis of rotation and on which rolls a friction disk fixed on one of the gudgeons of the mold.

in order either to achieve as uniform a casing wall thickness as possible or to obtain an enlarged accumulation of mat rial at particular points, for example around the inner portions of the terminals, it may be desirable during centrifugal casting to rotate the mold more rapidly upon one axis than upon the other. In a device of the kind referred to, this is accomplished by simple means, for example by a longitudinally displaceable mounting the friction disk on one gudgeon of the mold.

Centrifugal casting devi es are likewise conceivable i which the mold is rotated on more than two axes. With correct choice of speeds of rotation about each axis, these will afford an especially uniform casing wall, and many variations in distribution of material may be obtained by varying these speeds. However, experience has shown that molds rotatin on only two mutually perpendicular axes will definitely afford adequate uniformity of Wall thickness, and also, by regulation of speeds, permit the formation of enlarged deposit of material at the points where the fuse is exposed to greater mechanical stress. For their simplicity of construction, therefore, such devices would generally be preferred.

The device according to the invention will now be more fully described with reference to the accompanying drawing, given by way of illustration and not of 'ing material.

(a limitation, many changes in the details being possible without departing from the spirit of the invention.

In the drawing:

FIG. 1 shows a top view of a prefabricated link assembly;

FIG. 2 shows a front view of the same;

FIG. 3 shows a cross section of a mold in which the said assembly is being imbedded in quenching medium;

FIG. 4 shows a cross section of a mold for casting a casing;

FIG. 5 is a pictorial view of the final product of the foregoing operations;

FIG. 6 is a pictorial view of a device for centrifugal casting of a hollow cartridge casing;

FIG. 7 is a front view of the same; and

FIG. 8 is an end View of the same.

The assembly in FIGS. 1 and 2 consists of two terminals 1 and 2, in the form of knife-like contact tabs, to each of which a lateral appendage 3, 4 is attached. These appendages, whose hammerhead extremities extend beyond the confines of the fuse cartridge, serve to couple a manipulating handle with the finished cartridge. At their confronting ends, terminals 1 and 2 are connected by two fusible links 5 and 6. Between appendages 3, 4 and the points of attachment of the links 5, 6, the terminals 1, 2 have recesses 7 to be locate-d within the casing wall of the finished fuse cartridge.

The mold of FIG. 3 consists of two halves 8 and 9, for casting the core of porous arc-quenching material 10 enveloping the links 5, 6. These two halves accommodate the terminals 1 and 2, with appendages 3 and 4, and provide a cavity in the shape of the inner core around the links 5, 6 and their points of attachment to terminals 1 and 2. A part 11 in half 8 serves to admit quenching substance with a small quantity of binder added.

The mold of FIG. 4 for casting the casing or shell 12 similarly consists of two parts 13 and 14, accommodating the portions of terminals 1 and 2 projecting from the casing, and forms a cavity greater by the wall thickness of the casing than the core 10. The shell 12 integrally formed in this mold embraces the conductor members 1, 2 received therein.

The mold 13, 14 may be modified so as to enlarge its cavity at the inner portions of the terminals, so that a fuse cartridge cast in it may have somewhat the form represented in FIG. 5. As shown in FIGS. 68, the mold 15 receiving the prefabricated unit of FIGS. 1 and 2 has a cavity, around links 5, 6, conforming to the shape of a cartridge casing of the kind shown in FIG. 5. The mold 15 is provided with two gudgeons 16 and 17 on the same centerline as the fuse, and these are mounted in a frame 18. The frame 13 is supported by two gudgeons 19, 20, for rotation about an axis perpendicularly bisecting the centerline of gudgeons 16, 17, and can be driven in the direction of the arrow (FIG. 8). On one side, frame 18 has a disk 21 which turns with it about its axis of rotation and upon which there rolls a friction disk 22, non-rotatably mounted on gudgeon 16 of mold 115 but longitudinally adjustable thereon for example along a track 23 (FIG. 6).

The mold 15 has a cylindrical boss 24, directed into the cavity and visible in FIG. 8, for coring a hole to be afterwards used to introduce comminuted quenching material into the casing for forming the core 10 of FIGS. 2 and 3.

The mold 15 may in addition he provided with a closable port (not shown) for introduction of a predetermined quantity of synthetic resin serving as the cast- As will be apparent from FIG. 6 (see also FIG. 4), the shell 12 formed within the mold 15 is anchored to intermediate portions of the terminal memhers 1, 2 just beyond the ends joined to the fusible link 5, 6 which are to be imbedded in the porous core 10.

We claim as our invention:

1. A method of making a cartridge fuse, comprising the steps of producing a conductive unit including a pair of spaced-apart elongated conductor members having confronting ends joined by a fusible link, and consecutively forming two bodies of nonconductive material in nested relationship about said link and said confronting ends, one of said bodies being a porous inner core of arc-quenching material completely enveloping said link and said confronting ends, the other of said bodies being an integrally molded one piece shell of synthetic resin closely surrounding said core in direct contact with the entire core surface while letting outer extremities thereof project outwardly from the shell, the molding of said shell being carried out in a split mold having a cavity accommodating said link and said confronting ends, upon a gripping of said outer extremity between separable parts of the mold, with an all-around clearance corresponding to the combined thickness of said shell and said core.

2. A method as defined in claim 1 wherein said inner core is formed first, the step of forming said core including admixing with said arc-quenching material a minor proportion of a binder and molding the mixture about part of said conductive unit, said shell being molded about said core upon the setting of said binder.

3. A method of making a cartridge fuse, comprising the steps of producing a conductive unit including a pair of spaced-apart elongated conductor members having confronting ends joined by a fusible link, and consecutively forming two bodies of nonconductive material in nested relationship about said link and said confronting ends, one of said bodies being a porous inner core of arcquenching material extending around said link and said confronting ends, the other or" said bodies being an integrally molded shell of synthetic resin formed before said core and closely enveloping said core and embracing said conductor members while letting outer extremities thereof project outwardly from the shell, the step of forming said shell including placing aid conductive unit with the exception of said projecting extremities in a rotatable mold, partly filling said mold with moldable synthetic UNITED STATES PATENTS 1,862,317 6/32 Ringwald 200-420 1,875,031 8/32 Landau.

1,934,459 11/33 Prince et al. 200- 2,493,434 1/50 Yonkers 29155.5 2,681,398 1/54 Kozacka et a1. 200120 2,740,187 4/56 Jacobs et al 29--155.5 2,830,156 4/58 Burgess 200-120 2,847,707 8/58 Sullivan 18-26 2,892,061 6/59 Kozacka 20012O 2,895,031 7/59 Kozacka 200120 2,940,161 6/60 Elarde 29-155.5 2,946,092 7/60 Yoder 1826 WHITMORE A. WlLTZ, Primary Examiner.

RICHARD M. WOOD, JOHN F. CAMPBELL,

Examiners 

1. A METHOD OF MAKING A CARTRIDGE FUSE, COMPRISING THE STEPS OF PRODUCING A CONDUCTIVE UNIT INCLUDING A PAIR OF SPACED-APART ELONGATED CONDUCTOR MEMBERS HAVING CONFRONTING ENDS JOINED BY A FUSIBLE LINK, AND CONSECUTIVELY FORMING TWO BODIES OF NONCONDUCTIVE MATERIAL IN NESTED RELATIONSHIP ABOUT SAID LINK AND SAID CONFRONTING ENDS, ONE OF SAID BODIES BEING A POROUS INNER CORE OF ARC-QUENCHING MATERIAL COMPLETELY ENVELOPING SAID LINK AND SAID CONFRONTING ENDS, THE OTHER OF SAID BODIES BEING AN INTEGRALLY MOLDED ONE PIECE SHELL OF SYNTHETIC RESIN CLOSELY SURROUNDING SAID CORE IN DIRECT CONTACT WITH THE ENTIRE CORE SURFACE WHILE LETTING OUTER EXTREMITIES THEREOF PROJECT OUTWARDLY FROM THE SHELL, THE MOLDING OF SAID SHELL BEING CARRIED OUT IN A SPLIT MOLD HAVING A CAVITY ACCOMMODATING SAID LINK AND SAID CONFRONTING ENDS, UPON A GRIPPING OF SAID OUTER EXTREMITY BETWEEN SEPARABLE PARTS OF THE MOLD, WITH AN ALL-AROUND CLEARANCE CORRESPONDING TO THE COMBINED THICKNESS OF SAID SHELL AND SAID CORE. 